
theorem Th623:
Sum digits(2940,10) = 15
proof
  thus Sum digits(2940,10) = Sum <%0,4,9%>+Sum <%2%> by Th622,AFINSQ_2:55
  .= Sum <%0,4%> + Sum <%9%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 4) + Sum <%9%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 4 + 9) + Sum <%2%> by AFINSQ_2:53
  .= 13 + 2 by AFINSQ_2:53
  .= 15;
end;
